Pd colloid grafted mesoporous silica and its extraordinarily high catalytic activity for Mizoroki-Heck reactions

A Pd colloid grafted heterogeneous catalyst, with as low as 0.1 mol% Pd loading in mesoporous silica, was presented. In this composite, the palladium was evenly reduced by Si-H group to form metal colloids existing as isolated islands both on the inner and outer surfaces. The evenly dispersed catalyst species showed high catalytic activity with extremely low amounts of Pd catalysts for Mizoroki-Heck reactions. The large and open pore network, ultrahigh specific surface area and highly dispersed catalyst species made it one of the most active heterogeneous catalysts. The palladium colloid showed very high stability against leaching from the support and can be recycled for repeated use.